1. Field of the Invention
The present invention relates to autonomous vehicles that run in a work area. More particularly, the present invention relates to an autonomous vehicle that can run while recognizing the configuration of a work area.
2. Description of the Related Art
Various types of autonomous vehicles that travel autonomously while detecting the presence of an obstruction in the neighborhood are developed. An autonomous vehicle that carries out a predetermined work, for example scavenger, transportation, and the like while running along an object of interest such as a wall has been developed. One type of a conventional autonomous vehicle is disclosed in, for example, Japanese Patent Laying-Open No. 6-242825. Control is provided so that this conventional autonomous vehicle can run even when there is an interruption in a sidewall which is the object of interest such as in the case of a crossroads.
FIGS. 1 and 2 are diagrams for describing the problems of such a conventional autonomous vehicle. It is assumed that a conventional autonomous vehicle 300 travels in a trace-manner with a sidewall as a reference. When conventional autonomous vehicle 300 detects an interruption in a wall 301 during the tracer-travel, autonomous vehicle 300 will continue to run until a reference plane that allows tracer travel is detected. Therefore, autonomous vehicle 300 continues to run so as to collide with a wall plane 302 ahead even in the case where there is no wall plane on the line of extension of that followed wall plane 301.
Control is provided so that autonomous vehicle 300 stops running when no reference plane that allows tracer travel is detected at an elapse of a predetermined time from detection of interruption in a wall 303. When wall 304 is farther away from wall 303 by more than a predetermined distance as shown in FIG. 2, autonomous vehicle 300 will stop during the procedure to disable subsequent travel.
An autonomous vehicle that runs in a zigzag manner within a rectangle region is known. First, this zigzag travel will be described.
FIG. 3A is a diagram for describing the route of an autonomous vehicle when the direction of travel at a starting point A is parallel to the shorter side of the rectangle region. FIG. 3B is a diagram for describing the route of an autonomous vehicle when the direction of travel at starting point A is parallel to the longer side of the rectangle region.
Referring to FIG. 3A, the autonomous vehicle that begins to run straight forward from location point A in a direction parallel to the shorter side of the rectangle region arrives at location point B. The autonomous vehicle rotates 90 degrees clockwise at location point B to proceed a short distance straight forward up to location point C. The autonomous vehicle rotates 90 degrees clockwise at location point C to further proceed straight forward towards location point D. Then, the autonomous vehicle rotates 90 degrees counterclockwise and proceeds straight forward at respective location points D and E.
By repeating the movement of proceeding straight forward and turning 90 degrees as described above, the autonomous vehicle will run in a zigzag manner all over the rectangle region.
FIG. 3B shows the zigzag travel proceeding straight forward from a starting point A' in a direction parallel to the longer side of the rectangle region. The autonomous vehicle begins to run from point A' through points B', C', D' and E' to arrive at location point F'. By repeating the movement of proceeding straight forward and turning 90 degrees similar to that of FIG. 3A, the autonomous vehicle will cover the rectangle region in a zigzag manner.
In the above-described zigzag travel, the direction parallel to the path of AB and path A'B' is called the straight forward direction for the autonomous vehicle.
FIGS. 4A-4C are diagrams for describing the rectangle region in which the autonomous vehicle runs in a zigzag manner. FIG. 4A shows the first case where the rectangle region which is the work area is enclosed by a wall such as in a room. FIG. 4B shows the second case where only both sides of the rectangle region have walls as in a corridor. FIG. 4C shows the third case corresponding to an open region.
Referring to FIG. 4A, it is assumed that the user will have the autonomous vehicle conduct an operation such as scavenging starting from one corner of the work area. The autonomous vehicle detects respective distances L1 and L2 to the wall using a sensor. The detected distances are set as the respective dimension of the rectangle region where the zigzag travel is to be carried out.
In FIG. 4B, the user sets a length L1 corresponding to the longitudinal direction where there are no walls. Upon placing the autonomous vehicle at one corner of the work area to begin a predetermined operation, the autonomous vehicle detects a distance L2 to the wall using a sensor. The dimension of the rectangular region in which zigzag travel is to be carried out is set according to the detected distances L1 and L2.
In FIG. 4C, the user sets lengths L1 and L2 corresponding to a straight forward direction and an orthogonal directions thereto to start a predetermined operation. The autonomous vehicle sets the dimension of the rectangle region in which the zigzag travel is to be carried out according to distances L1 and L2.
As described with reference to FIGS. 3A and 3B, the direction of travel at the starting point is set to either a direction parallel to the shorter side or the longer side of the rectangle region to be scavenged.
The scavenger operation time required for covering the rectangle region is calculated for the respective cases shown in FIGS. 3A and 3B. The operation time is the sum of the time required for a straight forward travel and the time required for rotating 90 degrees. The operation time is represented by the following equation. EQU (Operation time)={(distance of one straight forward travel).times.(number of lanes to run)+(distance of lane change).times.(number of lanes-1)}/(running speed)+(time consumed for 90.degree. rotation).times.(number of U turns).times.2.
In the cases of 3A and 3B, it is assumed that the autonomous vehicle zigzags a rectangle region of 10 m.times.5 m at the operation width of 50 cm. The running speed is 30 cm/second, and the time required to turn 90 degrees is 2 seconds.
In the zigzag travel of FIG. 3A, (number of lanes to run)=20, and (number of U turns)=19. Substituting these into the above equation, (operation time)={5.times.20+0.5.times.19}/0.3+2.times.19.times.2=441 [second].
In the zigzag travel of FIG. 3B, (number of lanes to run)=10 and (number of U turns)=9. Substituting these into the above equation, (operation time)={10.times.10+0.5.times.9}/0.3+2.times.9.times.2=384 [second].
It is appreciated that there is a difference of approximately 60 seconds depending upon the direction of travel of the autonomous vehicle from the starting point of a rectangle work area of 10 m.times.5 m.
The time of 2 seconds for a 90.degree. rotation is the ideal time where there is no obstacle in the neighborhood. In practice, there is a possibility that the autonomous vehicle will move backward from the wall to rotate 90 degrees and then return to its former position in taking a U turn at the wall. Therefore, a greater time is required in practice.
When the time required for a 90.degree. rotation is 6 seconds, there is a difference of approximately 140 seconds according to the calculation of the above equation depending upon the direction of travel of the autonomous vehicle at the starting point of the operation.
For the sake of simplifying the calculation, the acceleration and deacceleration of the autonomous vehicle at the beginning and end of each straight run is not taken into account. Therefore, the difference will become greater when these issues are taken into consideration.
Thus, it is appreciated that the direction of travel of the autonomous vehicle in commencing a zigzag travel greatly affects the operation time.
An autonomous vehicle that is made to conduct an operation by remote control will be described hereinafter. The user has an autonomous vehicle conduct an operation (this operation includes travel) within a work area using a controller that provides remote control of the autonomous vehicle. Upon completion of the operation, the series of the work operation is recorded in a memory card. By having the autonomous vehicle conduct an operation using a controller and recording the series of operation, the autonomous vehicle can be made to learn a work operation.
The autonomous vehicle can repeat the same operation by reproducing the learned operation. However, the conventional autonomous vehicle cannot run in an area other than the predetermined region stored in the memory.
The following technique can be derived by combining the above-described art.
When an autonomous vehicle detects an interruption in the wall while running along a wall, the depth of the concave of that wall is measured. The travel at the concave region is determined according to the depth of the concave. The travel that can be selected in this case includes a zigzag travel at the concave region, a horizontal travel at the concave region, and a straight forward travel ignoring the concave region. However, no particular consideration is provided of the selection in the direction of advance of the zigzag travel.